1. Field of the Invention
This invention relates to a scroll-type fluid displacement apparatus and, more particularly, to a regulating mechanism for regulating an axial movement of a driving mechanism of the apparatus.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a scroll-type fluid displacement apparatus, such as a scroll-type refrigerant compressor in accordance with the prior art.
In FIGS. 1 and 2, for purposes of explanation only, the left side of the figures will be referred to as the forward end or front of the compressor, and the right side of the figures will be referred to as the rearward end or rear of the compressor.
As shown in FIG. 1, compressor 300 includes compressor housing 310 having front end plate 311 and cup-shaped casing 312 which is secured to the rear end surface of front end plate 311 by a plurality of bolts 313. An opening 311a is formed in the center of front end plate 311 for penetration or passage of a drive shaft 314, which is made of steel. An opening end of cup-shaped casing 312 is covered by front end plate 311, and the mating surfaces between front end plate 311 and cup-shaped casing 312 are sealed by a first O-ring 315. First annular sleeve 311b forwardly projects from a periphery of opening 311a so as to surround a front end portion of drive shaft 314 and define shaft seal cavity 311c therein. A mechanical seal element 314d is disposed within shaft seal cavity 311c and is mounted about drive shaft 314.
Drive shaft 314 is rotatably supported by first annular sleeve 311b through radial needle bearing 316, which is positioned within the front end of first annular sleeve 311b. Second annular sleeve 311d rearwardly projects from the periphery of opening 311a so as to surround an inner end portion of drive shaft 314.
Inner block 320 having front annular projection 321 and rear annular projection 322 is disposed within an interior of housing 310. The interior of housing 310 is defined by the inner wall of cup-shaped casing 312 and the rear end surface of front end plate 311. Inner block 320 is fixedly attached to front end plate 311 at its front annular projection 321 by a plurality of bolts 317, so that front annular projection 321 of inner block 320 surrounds second annular sleeve 311d of front end plate 311, and so that a front end surface of front annular projection 321 is in contact with the rear end surface of front end plate 311.
Drive shaft 314 has cylindrical rotor 314a which is integral with and coaxially projects from an inner end surface of drive shaft 314. A diameter of cylindrical rotor 314a is greater than that of drive shaft 314. Cylindrical rotor 314a is rotatably supported by inner block 320 through radial plane bearing 325 which is fixedly disposed within opening 323 centrally formed through inner block 320. Radial plane bearing 325 is fixedly disposed within opening 323 by, for example, forcible insertion. Pin member 314b is integral with, and projects from, a rear end surface of cylindrical rotor 314a. An axis of pin member 314b is radially offset from an axis of cylindrical rotor 314a, i.e., an axis of drive shaft 314, by a predetermined distance.
An electromagnetic clutch 318, which is disposed around first annular sleeve 311b, includes a pulley 318a rotatably supported on sleeve 311b through ball bearing 318b, an electromagnetic coil 318c disposed within an annular cavity of pulley 318a, and an armature plate 318d fixed on an outer end of drive shaft 314, which extends from sleeve 311b. Drive shaft 314 is connected to and driven by an external power source through electromagnetic clutch 318.
The interior of housing 310 further accommodates a fixed scroll 330, an orbiting scroll 340, and a rotation preventing mechanism (such as Oldham coupling mechanism 350), which prevents rotation of orbiting scroll 340 during operation of the compressor.
Fixed scroll 330 includes circular end plate 331, a first spiral element 332 affixed to or extending from a front side surface of circular end plate 331, and an outer peripherial wall 333 forwardly projecting from an outer periphery of circular end plate 331. Outer peripheral wall 333 of fixed scroll 330 is fixedly attached to rear annular projection 322 of inner block 320 by a plurality of bolts 319, so that a rear end surface of rear annular projection 322 of inner block 320 is in contact with a front end surface of outer peripheral wall 333 of fixed scroll 330. Thus, fixed scroll 330 is fixedly disposed within the interior of housing 310.
A second O-ring 334 is elastically disposed between an outer rear peripheral surface of circular end plate 331 and an inner peripheral surface of cylindrical portion 312a of cup-shaped casing 312 to seal the mating surfaces therebetween. Thus, a first chamber section 360 is defined by circular end plate 331 of fixed scroll 330 and a rear portion 312b of cup-shaped casing 312. A third O-ring 324 is elastically disposed between an outer rear peripheral surface of rear annular projection 322 of inner block 320 and the inner peripheral surface of cylindrical portion 312a of cup-shaped casing 312 to seal the mating surfaces therebetween. Thus, a second chamber section 370 is defined by circular end plate 331 of fixed scroll 330, a part of cylindrical portion 312a of cup-shaped casing 312 and inner block 320. Also a third chamber section 380 is defined by inner block 320, a part of cylindrical portion 312a of cup-shaped casing 312 and front end plate 311.
Inlet port 310a is formed on cylindrical portion 312a of cup-shaped casing 312 at a position corresponding second chamber section 370 to place second chamber section 370 in communication with the exterior of compressor 300. Outlet port 310b is formed on cylindrical portion 312a of cup-shaped casing 312 at a position corresponding third chamber section 380 to place third chamber section 380 in communication with the exterior of compressor 300.
A plurality of fluid passages (not shown) are axially formed through outer peripheral wall 333 of fixed scroll 330 and rear annular projection 322 of inner block 320 along the periphery thereof so as to link first chamber section 360 to third chamber section 380. Though the above fluid passages are not shown in the drawings, they are located in the vicinity of holes 333a, through which shaft portions of bolts 319 penetrate.
A hole or discharge port 335 is formed through circular end plate 331 of fixed scroll 330 at a position near the center of first spiral element 332. Reed valve member 336 cooperates with discharge port 335 at a rear end surface of circular end plate 331 of fixed scroll 330 to control the opening and closing of discharge port 335 in response to a pressure differential between first chamber section 360 and a central fluid pocket 390a. Retainer 337 is provided to prevent excessive bending of reed valve member 336 when discharge port 335 is opened. An end of reed valve member 336 is fixedly secured to circular end plate 331 of fixed scroll 330 by a single bolt 338, together with an end of retainer 337.
Orbiting scroll 340, which is located in second chamber section 370, includes circular end plate 341 and a second spiral element 342 affixed to or extending from a rear end surface of end plate 341. Second spiral element 342 of orbiting scroll 340 and first spiral element 332 of fixed scroll 330 interfit at an angular offset of 180.degree. and a predetermined radial offset to make a plurality of line contacts. Therefore, at least one pair of sealed-off fluid pockets 390 are defined between spiral elements 332 and 342.
Referring also to FIG. 2, orbiting scroll 340 further includes an annular boss 343, which forwardly projects from a central region of a front end surface of circular end plate 341. Bushing 344 is rotatably disposed within boss 343 through radial plane bearing 345. Radial plane bearing 345 is fixedly disposed within boss 343 by, for example, forcible insertion. Bushing 344 has a hole 344a axially formed therethrough. An axis of hole 344a is radially offset from an axis of bushing 344. As described above, pin member 314b is integral with, and projects from, the rear end surface of cylindrical rotor 314a of drive shaft 314. The axis of pin member 314b is radially offset from the axis of cylindrical rotor 314a, i.e., the axis of drive shaft 314 by a predetermined distance.
Pin member 314b is rotatably disposed within hole 344a of bushing 344. A terminal end portion of pin member 314b projects from a rear end surface of bushing 344, and snap ring 346 is fixedly secured to the terminal end portion of pin member 314b to prevent axial movement of pin member 314b within hole 344a of bushing 344. Thus, drive shaft 314, pin member 314b and bushing 344 form a driving mechanism for orbiting scroll 340. Counter balance weight 347 is disposed within second chamber section 370 at a position forward from circular end plate 341 of orbiting scroll 340, and is connected to a front end of bushing 344. Annular flange 314c is made of steel, for example, and is formed at a position which constitutes a boundary between the inner end portion of drive shaft 314 and cylindrical rotor 314a. A diameter of annular flange 314c is greater than the diameter of cylindrical rotor 314a.
First thrust plane bearing 326 is fixedly disposed within an annular cut-out portion 311e, which is formed at an outer peripheral region of the rear end surface of second annular sleeve 311d, by a plurality of fixing pins 326a. A rear end surface of first thrust plane bearing 326 slightly projects from the rear end surface of second annular sleeve 311d. The rear end surface of first thrust plane bearing 326 faces the front end surface of annular flange 314c. A rear end surface of fixing pins 326a is forward of the rear end surface of first thrust plane bearing 326. First thrust plane bearing 326 may be in frictional contact with annular flange 314c, and may receive a forward thrust force through annular flange 314c.
Second thrust plane bearing 327, which is substantially identical to first thrust plane bearing 326, is fixedly disposed within a shallow annular depression 320a, which is formed at the from end surface of inner block 320 along a periphery of opening 323, by a plurality of fixing pins 327a. Second thrust plane bearing 327 surrounds a front end portion of radial thrust bearing 325, and faces the rear end surface of annular flange 314c. A front end surface of second thrust plane bearing 327 slightly projects from the from-end surface of inner block 320. A front end surface of fixing pins 327a is rearward of the from top end surface of second thrust plane bearing 327. Second thrust plane bearing 327 may be in frictional contact with annular flange 314c, and may receive a rearward thrust force through annular flange 314c.
With reference to FIG. 3, first thrust plane bearing 326 includes a first annular element 326b and second annular element 326c which is disposed on one end surface of first annular element 326b. First annular element 326b is made of, for example, steel and second annular element 326c is made of, for example, phosphor bronze (which is softer than steel). First and second annular elements 326b and 326c are fixedly bonded to each other by, for example, sintering. First thrust plane bearing 326 further includes a plurality of radial grooves 326d which are formed at an axial outer end surface of second annular element 326c.
With reference to FIG. 2 in addition to FIG. 3, second annular element 326c of phosphor bronze faces annular flange 314c of steel, so that first thrust plane bearing 326 can be in frictional contact with annular flange 314c in a soft-to-hard-metal contact. As a result, abrasion resistance of the frictional contact surfaces between first thrust plane bearing 326 and annular flange 314c is increased. As shown in FIG. 3, thickness L.sub.1 of first annular element 326b may be designed to be sufficiently greater than thickness L.sub.2 of second annuler element 326c. For example, thickness L.sub.1 of first annular element 326b may be designed to be 1.2 mm and thickness L.sub.2 of second annular element 326c may be designed to be 0.3 mm. Furthermore, the construction of second thrust plane bearing 327 is similer to that of first thrust plane bearing 326 and, therefore, an explanation thereof is omitted.
Referring again to FIG. 2, fluid passage 371 is axially formed through pin member 314b and cylindrical rotor 314a. One end of fluid passage 371 is open to an axial air gap 372 created between the rear end surface of bushing 344 and the front end surface of circular end plate 341 of orbiting scroll 340. The other end of fluid passage 371 is open to a radial air gap 381 created between an inner peripheral surface of second annular sleeve 311d and an outer peripheral surface of the inner end portion of drive shaft 314. Radial air gap 381 is linked to a hollow space 382, which is defined by second annular sleeve 311d of front end plate 311 and front annular projection 321 of inner block 320, through either an axial air gap 383 created between annular flange 314c and first thrust plane bearing 326 or radial grooves 326d formed at the axial outer end surface of second annular element 326c of first thrust plane bearing 326. Hollow space 382 is linked to a lower portion of third chamber section 380 through conduit 328 which is radially formed through inner block 320. Capillary tube element 329 is fixedly disposed within conduit 328. Filter member 329a is fixedly attached to a lower end of capillary tube element 329.
Aforementioned Oldham coupling mechanism 350, functioning as the rotation preventing device for orbiting scroll 340, is disposed between circular end plate 341 of orbiting scroll 340 and rear annular projection 322 of inner block 320. By providing Oldham coupling mechanism 350, the rotation of drive shaft 314 causes orbiting scroll 340 to orbit without rotating.
With reference to FIG. 4, radial plane bearing 325 includes a first annular cylindrinal element 325a and second annular cylindrical element 325b, which is radially surrounded by an inner peripheral surface of first annular cylindrical element 325a. First annular cylindrical element 325a is made of, for example, steel. Second annular cylindrical element 325b is made of, for example, phosphor bronze (which is softer than steel). First and second annular cylindrical elements 325a and 325b are fixedly bonded to each other by, for example, sintering.
Referring further to FIG. 2, an inner peripheral surface of second annular cylindrical element 325b of phosphor bronze faces an outer peripheral surface of cylindrical rotor 314a, which is made of steel. This radial plane bearing 325 is in frictional contact with cylindrical rotor 314a in a soft-to-hard-metal contact. As a result, the abrasion resistance of the frictional contact surfaces between radial plane bearing 325 and cylindrical rotor 314a is increased. As shown in FIG. 4, thickness L.sub.3 of first annular cylindrical element 325a is designed to be sufficiently greater than thickness L.sub.4 of second annular cylindrical element 325b. For example, thickness L.sub.3 of first annular cylindrical element 325a may be designed to be 1.7 mm and thickness L.sub.4 of second annular cylindrical element 325b may be designed to be 0.3 min. Furthermore, the construction of radial plane bearing 345 is similar to that of radial plane bearing 325 and, therefore, an explanation thereof is omitted.
Because of cost, weight reduction, and durability considerations, radial plane bearings 325 and 345 and first and second thrust plane bearings 326 and 327 (as described above) are typically superior to conventional bearings, such as a ball-type bearings.
During operation, as orbiting scroll 340 orbits, the line contacts between spiral elements 332 and 342 move toward the center of these spiral elements along the spiral curved surfaces of spiral elements 332 and 342. This causes the fluid pockets 390 to move to the center with a consequent reduction in volume and compression of the fluid (e.g., refrigerant) in the fluid pockets 390. Refrigerant gas, which is introduced from a component, such as an evaporator (not shown) of a refrigerant circuit (not shown), through fluid inlet port 310a, is taken into the fluid pockets 390 formed between spiral elements 332 and 342 from the outer end portion of the spiral elements.
The refrigerant gas taken into the fluid pockets 390 is then compressed and discharged through discharge port 335 into first chamber section 360 from the central fluid pocket 390a of spiral elements 332 and 342. Thereafter, the refrigerant gas in first chamber section 360 flows to third chamber section 380 through the aforementioned fluid passages (not shown), which are axially formed through outer peripheral wall 333 of fixed scroll 330 and rear annular projection 322 of inner block 320. The refrigerant gas flowing into third chamber section 380 further flows through fluid outlet port 310b to another component, such as a condenser (not shown) of the refrigerant circuit (not shown).
Referring to FIGS. 1 and 2, the lubricating oil accumulated at a bottom portion of the interior of first chamber section 360 flows into the bottom portion of the interior of third chamber section 380 through the aforementioned fluid passages (not shown), which are axially formed through outer peripheral wall 333 of fixed scroll 330 and rear annular projection 322 of inner block 320. The lubricating oil in the bottom portion of the interior of third chamber section 380 is conducted into a hollow space 373 of second chamber section 370 created between inner block 320 and circular end plate 341 of orbiting scroll 340 by virtue of the pressure differential between third chamber section 380 and second chamber section 370 via conduit 328, hollow space 382, either axial air gap 383 or radial grooves 326d of first thrust plane bearing 326 (shown in FIG. 3), fluid passage 371, axial air gap 372, and radial air gaps created between boss 343 and radial plane bearing 345 and between bushing 344 and radial plane bearing 345. The lubricating oil conducted into hollow space 373 flows through second chamber section 370 at a position which is outside spiral elements 332 and 342, and past Oldham coupling mechanism 350 to lubricate mechanism 350.
Further, a part of the lubricating oil which is conducted to radial air gap 381 flows to shaft seal cavity 311c, and lubricates the internal frictional surfaces of mechanical seal element 314d and the frictional surfaces between mechanical seal element 314d and drive shaft 314.
Moreover, a part of the lubricating oil which is conducted to hollow space 382 flows through radial grooves 327d of second thrust plane bearing 327 (shown in FIG. 3), and then flows into hollow space 373 of second chamber section 370 through a radial air gap created between an outer peripheral surface of radial plane bearing 325 and an inner peripheral surface of opening 323 of inner block 320 and through a radial air gap created between an inner peripheral surface of radial plane bearing 325 and an outer peripheral surface of cylindrical rotor 314a.
A part of the lubricating oil which is conducted to hollow space 373 flows into axial air gap 372 through a radial air gap created between an outer peripheral surface of radial plane bearing 345 and an inner peripheral surface of boss 343 and through a radial air gap created between an inner peripheral surface of radial plane bearing 345 and an outer peripheral surface of bushing 344.
As the lubricating oil flows from the bottom portion of the interior of third chamber section 380 to second chamber section 370 as described above, the frictional surfaces of the internal components of the compressor, such as the frictional surface between bushing 344 and radial plane bearing 345 are effectively lubricated by the lubricating oil.
According to these features, when the compressor is assembled, positive tolerant axial air gaps must be created between the following pairs of adjacent surfaces (shown in FIG. 2) in order to prevent defective interferences therebetween.
(A) the adjacent surfaces of bushing 344 and circular end plate 341 of orbiting scroll 340; PA1 (B) the adjacent surfaces of counter balance weight 347 and boss 343 of orbiting scroll 340; PA1 (C) the adjacent surfaces of counter balance weight 347 and Oldham coupling mechanism 350; PA1 (D) the adjacent surfaces of counter balance weight 347 and inner block 320; PA1 (E) the adjacent surfaces of annular flange 314c and second annular sleeve 311d; and PA1 (F) the adjacent surfaces of annular flange 314c and inner block 320;
Further, in contrast with a conventional bearing device, such as a radial ball bearing which includes inner and outer races and a plurality of ball elements rollingly disposed between the races, no preventing element for preventing axial movement of drive shaft 314 is provided between drive shaft 314 and radial plane bearings 325 and 345 and between drive shaft 314 and radial needle bearing 316. As a result, during operation of the compressor 300, drive shaft 314 may forwardly and rearwardly slide along the inner peripheral surfaces of radial plane bearings 325 and 345 and the inner peripheral surface of radial needle bearing 316 due to the positive tolerant axial air gaps described above.
Accordingly, during operation of the compressor 300, as drive shaft 314 rearwardly moves, a collision may occur between one or more of the above-described adjacent surfaces (A), (B), (C) and (F) having the smallest positive tolerant axial air gap. As drive shaft 314 forwardly moves, a collision may occur between one or more of the above-described adjacent surfaces (D) and (E) having the smaller positive tolerant axial air gap. These collisions may cause an offensive noise and an abnormal abrasion at the colliding adjacent surfaces.
In order to prevent the above defects, as illustrated in FIG. 2, first and second thrust plane bearings 326 and 327 are provided at the rear end surface of second annular sleeve 311d and the front end surface of inner block 320, respectively. In addition, the positive tolerant axial air gap 383 created between the front end surface of annular flange 314c and the rear end surface of first thrust plane bearing 326 is designed to be smaller than the positive tolerant axial air gap created between the adjacent surfaces (D). Also, the positive tolerant axial air gap created between the rear end surface of annular flange 314c and the front end surface of second thrust plane bearing 327 is designed to be smaller than the positive tolerant axial air gap created between any of the pairs of adjacent surfaces (A), (B) and (C). As a result, the forward and rearward movements of drive shaft 314 are limited by first and second thrust plane bearings 326 and 327, respectively. Since first and second thrust plane bearings 326 and 327 are constructed as illustrated in FIG. 3, offensive noise and abnormal abrasion are reduced.
However, the positive tolerant axial air gap 383 created between the front end surface of annular flange 314c and the rear end surface of first thrust plane bearing 326 becomes relatively large, for example, 0.1 mm-0.5 mm, due to precision limitations during the machining of inner block 320 having front annular projection 321, front end plate 311 having second annular sleeve 311d, and drive shaft 314 having annular flange 314c. Similarly, the positive tolerant axial air gap created between the rear end surface of annular flange 314c and the front end surface of second thrust plane bearing 327 also becomes relatively large, for example, 0.1 mm-0.5 mm, due to also the above-referenced machining precision limitations.
Thus, offensive noise and abnormal abrasion at the contact surfaces between annular flange 314c and first thrust plane bearing 326 and between annular flange 314c and second thrust plane bearing 327 are not sufficiently reduced.